When intertwining and electrically connecting insulated wires each having an insulated sheath, a variety of connecting methods have been adopted (for example, refer to Patent Documents 1 and 2). That is, the insulated sheaths of parts to be connected are stripped by a predetermined length, thereby exposing conductors. Then, the exposed conductors are soldered each other or are twisted together and connected by hand.
For example, as shown in FIG. 11, according to a connecting method disclosed in Patent Document 1, a rotary connector 100 that has an inlet 101, which has a cylindrical shape so as to have an enlargement, and two holes 102 having predetermined angles and a rotary shaft 103 is attached thereto is used to insert two cords into the holes and to rotate the rotary shaft. Thereby, the two cords are rotated at the same time, so that the two cords are intertwined and connected.
Also, as shown in FIG. 12, a connecting method disclosed in Patent Document 2 is a method of making an interlocking spiral twist connection between two wires 203, 204 and includes steps of positioning the wires 203, 204 in side by side relationship in cavity portions in both members 201, 202 and providing relative rotation between both members 201, 201 of a two-member connector. The cavity portions have such a configuration that the wires 203, 204 can be introduced into the cavity portions only in side by side relationship in the cavity portions when the wires are in a specific orientation relative to the cavity portions. The relative rotation of the two members 201, 202 causes the respective wires 203, 204 to be jammed against inner surfaces of the respective cavities. Also, a braking effect on the wires 203, 204 for controlling relative longitudinal movement between the wires under relative rotation and a converging force on the members 201, 202 are kept. Also, reference numerals 203A, 204A indicate accommodation parts in the connector.
Also, in recent years, an ultrasonic bonding has been adopted from a standpoint of a simple and secure operation. For example, according to a method shown in FIGS. 13(A) to 13(D), insulated sheaths of a plurality of insulated wires 301 to 304 are stripped to expose conductors 301A to 304A, which are then simply arranged in parallel (which also includes a parallel superimposed configuration). The exposed conductors arranged in parallel are subject to ultrasonic bonding, so that the conductors 301A to 304A are connected.
When the ultrasonic bonding is performed as described above, connection strength may be problematic in some cases. Specifically, a part of the conductors may be detached due to the insufficient connection strength.
Therefore, a connecting method of insulated wires as disclosed in Patent Document 3 has been suggested. That is, according to this connecting method of insulated wires, as shown in FIGS. 14(A), 14(B), 15(A) and 15(B), insulated sheaths of a plurality of insulated wires 401 to 404 are stripped by a predetermined length, respectively, thereby exposing conductors 401A to 404A. The exposed conductors 401A to 404A are twisted together in the same direction. Then, the twisted parts are welded and connected by ultrasonic bonding. Thereby, when electrically connecting the plurality of insulated wires 401 to 404, it is possible to secure the sufficient connection strength even though the conductors 401A to 404A are connected by the ultrasonic bonding.